Look! A book is on the floor. Whose is it?—It ______ be Rick’s. It has his name on it.

The number of foreign students attending Chinese universities ________ rising steadily since1990.

We’ll go shopping if it ________ rain tomorrow.

It’s important __________ us students _______ carefully in class.

Would you like to go to the cinema with me?—Yes, I’d love to. But I ______ the film twice.